The invention generally relates to valves for separating product media in pipes of a product-carrying system. More specifically, the invention relates to a valve for separating product media in pipes of a product-carrying system which has a sealing diaphragm in order to seal a valve housing interior of the valve on the drive side.
A valve of this type is known, for example, from the Südmo Holding GmbH, Riesbürg, company brochure “Südmo SVP Ventile Modell 2000, Ventiltechnik für jeden Einsatzbereich [Südmo SVP model 2000 valves, valve technology for any application]”, 2006, page 2.
The known valve is used in a product-carrying system in order to separate product media flowing through pipes of the product-carrying system from one another. Such a product-carrying system can be, for example, a food technology system which conveys flowable product media, such as, for example, yogurt or juice, along the pipes.
The known valve has a valve body which is inserted into a valve housing and is in the form of a shut-off member in order to seal off the pipe connecting branches of the valve housing, which branches are connected to the pipes of the food technology system, from one another. The shut-off member of the valve body is movable between an open valve position and a closed valve position by a drive element. In the open valve position, the product media from one pipe connecting branch can flow via the valve housing interior into the other pipe connecting branch of the valve housing. In the closed valve position, the shut-off member seals off the pipe connecting branches from one another, as a result of which the flow of product medium through the valve housing interior is interrupted.
The known valve operates under aseptic conditions in particular in food technology systems, and therefore hermetic sealing off of the valve housing interior from the surroundings is required. For this purpose, the known valve has a sealing diaphragm which seals the valve housing interior on the drive side. The sealing diaphragm has a radially extending diaphragm body with a central opening and is fitted into the valve in such a manner that the drive element which is connected to the shut-off member runs through the opening in the diaphragm body. In order to retain the sealing diaphragm in the valve in a stable position, a radially outer edge region of the diaphragm body is clamped radially between an axially immovable receiving element and the valve housing, and a radially inner edge region of the diaphragm body is clamped axially between a first and a second element of the drive element. The known sealing diaphragm is manufactured as a single piece from elastomer, for example from ethylene-propylene-diene elastomer, and a strength-increasing braided textile material is embedded into the diaphragm body on the drive side. The material of the sealing diaphragm is widened in a bead-like manner in the region of the radially inner and outer edge regions in order to retain the sealing diaphragm such that, during the operation of the valve, the sealing diaphragm is prevented from slipping under exposure to tensile and pressure loads. Furthermore, the widened, radially inner and radially outer edge regions prevent product media from moving behind the sealing diaphragm in the regions in which the latter is clamped.
One disadvantage of the sealing diaphragm is that the material thereof is not of stable design mechanically, and the service life of the elastomer is limited under high temperature influences and pressure peaks. As a result, upon load changes which occur repeatedly during the operation of the valve, the sealing diaphragm may have fine hairline cracks in the clamping regions thereof and in the exposed diaphragm body and may also tear without previous formation of hairline cracks. This causes frequent servicing of the valve necessitating shutdown times and consequently increased operating costs for the food technology system.
A further disadvantage is that the diaphragm body of the sealing diaphragm is not of dimensionally stable design, and therefore an additional element, the textile fabric, has to be provided to increase the strength of the diaphragm body. The central embedding of the textile fabric into the diaphragm body is difficult to bring about during production and leads to production of the sealing diaphragm being costly.
Another disadvantage is that the elastomer is thermally resistant only in a limited temperature range. It must be taken into account in this case that the valve housing interior and the valve body are subjected to very hot cleaning media, and also to hot steam. The temperature may cause fine hairline cracks to appear here in the diaphragm body. The damage to the elastomer caused by temperature considerably restricts the use of the valve under aseptic conditions.
In particular, evermore exacting requirements are imposed on the thermal stability of the sealing diaphragm in order to reduce servicing-induced interruptions due to the sealing diaphragm being exchanged.